The research goal for the coming year will be a continuation of the comparison of inducible and non-inducible mouse 3T3 cells transformed by the ts-a mutant of polyoma virus. Hybridization experiments between the separated strands from polyoma fragments (obtained after Hemophilus parainfluenzae II digestion) and excess nuclear and cytoplasmic RNA of the various lines have been started. These experiments will allow the construction of maps for the primary (nuclear) transcripts and the porcessed transcripts reaching the cytoplasm. Since it was found that transcription of the L strand is initiated in the inducible lines after shift to 32 degrees C, similar shift experiments are planned in the presence of inhibitors of DNA synthesis. Such experiments should indicate whether viral DNA synthesis is required for the initiation of L strand transcription. To determine whether the viral sequences integrated into the host DNA are identical in inducible and non-inducible cells the representation of different Hpall-polyoma fragments in the cellular DNA will be determined in reassociation kinetics experiments.